LONDON (Reuters) - Sky said it would enter the UK mobile market with a SIM-only deal that allows data allowances to roll over each month, and offers free calls to the 11 million British households that take its TV services.

It was "time to shake up" the mobile market, particularly in data, where many customers paid for more than they used because they were worried about exceeding their allowance, the pay-TV group said on Tuesday.

Sky is the last of Britain's big four broadband providers to offer mobile to its customers, giving it the full "quad play" offer, which also includes TV and fixed-line telecoms.

Stephen van Rooyen, Sky's UK and Ireland chief executive, said the company had asked more than 30,000 potential customers what they wanted from a mobile service, and more flexibility on data was top of the list.

"We've designed it based on what people told us they want - it's easy, flexible and transparent and it puts the customer in control," he said

He declined to give any targets for customer sign ups, but said Sky households had on average two mobile contracts each, giving a potential market of about 23 million.